binary.Write(buf, binary.BigEndian, uint32(headerLength))
	prelude := buf.Bytes()
	binary.Write(buf, binary.BigEndian, crc32.ChecksumIEEE(prelude))
	buf.Write(header)
	message := buf.Bytes()
	binary.Write(buf, binary.BigEndian, crc32.ChecksumIEEE(message))

	fmt.Println(buf.Bytes())
}

func genProgressHeader() {
	buf := new(bytes.Buffer)

	buf.WriteByte(13)

	if err != nil {
		return err
	}
	key, err := hex.DecodeString(keyHex[8:])
	if err != nil {
		return err
	}
	// Verify that CRC is ok.
	want := binary.LittleEndian.Uint32(id)
	got := crc32.ChecksumIEEE(key)
	if want != got {
		return fmt.Errorf("Invalid key checksum, want %x, got %x", want, got)
	}

	stream, err := sio.AES_256_GCM.Stream(key)
	if err != nil {
		return err
	}

		w, err := zw.CreateRaw(&zip.FileHeader{
			Name:               name,
			Method:             zip.Store,
			CompressedSize64:   uint64(len(data)),
			UncompressedSize64: uint64(len(data)),
			CRC32:              crc32.ChecksumIEEE(data),
		})
		if err != nil {
			log.Fatal(err)
		}
		if _, err := w.Write(data); err != nil {
			log.Fatal(err)
		}
		seen[name] = true
		return nil
	})
	if err != nil {
		log.Fatal(err)
	}